In applications requiring the pumping of slurry materials, a generally encountered problem is that of preventing particulate matter in the slurry from fouling the operation of a pump. For example, in systems requiring the use of a coal-water slurry (CWS) fuel, the coal suspension includes a heavy, abrasive particulate matter. This coal particulate is prone to abrading bearing surfaces in the pump, and to settling in and clogging pump chambers and apertures.
A diaphragm pump, of the type wherein a pumping, motive fluid is sealingly separated from the pumped material by a flexible diaphragm, may be beneficially used in applications where the pumped material comprises a slurry. Such a pump, due to the separating function performed by the diaphragm, presents the advantage of mechanically isolating the particulate matter in the slurry from much of the pump mechanism. Diaphragm pumps, however, still suffer the disadvantage of internal clogging due to the settling of the particulate matter in the pump chambers and apertures.
The pumping of slurry materials at high rates and pressures poses special problems in addition to those described above. In particular, the settling qualities of the high-density particulate matter in the slurry often results in an uneven distribution of this particulate matter within a pumping chamber in the diaphragm pump. This uneven distribution of the particulate matter results in an uneven distribution of an internal, hydraulic pumping pressure on the flexible diaphragm. At high rates and pressures, this uneven distribution of the hydraulic pumping pressure causes premature wear and failure of the diaphragm.